Disc drives are well known in the industry. Such drives use rigid discs coated with a magnetizable medium for storage of digital information in a plurality of concentric data tracks. Typically, disc drives include a disc pack including a plurality of concentric discs mounted on a spindle motor which causes the discs to spin. Heads carrying transducer elements are supported via a suspension assembly relative to the disc surfaces to read and or write digital information to the disc surfaces. Known transducer elements include magnetoresistive ("MR") and inductive transducer elements.
Heads include a slider supported via the suspension assembly coupled to an actuator assembly Sliders include an air bearing surface which faces the disc surface. As the disc rotates, the disc drags air past the slider along the air bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the air bearing surface, the pressure between the disc and the air bearing surface increases, which creates a hydrodynamic lifting force that causes the slider to lift directly above the disc surface to read and/or write data to the surface of the disc. A fixed preload force is supplied to the slider via the suspension assembly to bias the head toward the disc surface. Prior to rotation of the disc, the slider rests on the disc surface. The slider is not lifted from the disc until the hydrodynamic lifting force, caused by rotation of the disc, is sufficient to overcome preload force holding the slider to the disc surface.
The hydrodynamic properties of the slider are affected by the speed of rotation of the disc, the design of the air bearing surface of the slider, and the preload force supplied to the slider via the suspension assembly. Areal disc drive density is increasing and thus, desired slider fly height is decreasing. The decrease in slider fly height requires better control of fly height variations to maximize recording performance without sacrificing mechanical reliability. With typical slider fly heights approaching 1 .mu.inch and less, conventional methods of controlling fly height variations are approaching their capability limits. Hence it is desirable to find new methods of improvising dive performance, manufacturing yields and mechanical reliability for disc drives.
Increased preload tends to increase wear and damage to the head and degrade mechanical reliability since a greater force is supplied to the head during contact starts and stops (CCS) and operation. Increased preload also increases the stiction force which increases power required to rotate the spindle motor and discs.
It is desirable to provide a suspension system having desired fly-height attributes without degradation of mechanical reliability and performance. The present invention addresses these and other problems, and offers other advantages over the prior art.